1. Technical Field
The present invention relates in general to an improved composition of matter and, in particular, to a novel composition of matter comprising a pure carbon isotropic alloy consisting of a plurality of allotropic forms of carbon.
2. Description of the Related Art
Elemental carbon has many different allotropic forms and applications. This wide variety of allotropic forms is attributable to carbon being the only element in the periodic table known to have isomers with 0, 1, 2, or 3 dimensions. The carbon atom can hybridize electronic states in several different valence bonds which allows for a variety of different atomic bonding configurations. The isomers can have sp, sp2, or sp3 hybridization in the valence electron orbitals. Some of the more common forms of carbon are graphite, charcoal, carbon fibers, and diamond. Many other allotropes of carbon exist, some of which have been discovered as recently as within the last 20 years.
In the 1980s, carbon fullerenes were discovered. These molecules are ellipsoidal shaped and typically contain 60 carbon atoms with near-planar sp2 hybridization. Each molecule resembles a soccer ball in configuration with a collection of pentagonal and hexagonal rings. Larger fullerenes with 70 or 84 carbon atoms do exist but are less common and more ellipsoidal in shape. Carbon fullerenes have been made using an arc-discharge method to generate carbon plasma and then a controlled deposition in a furnace.
Carbon nanotubes are another form of carbon allotrope which also have sp2 near-planar hybridization, but form high aspect ratio, hollow tubes. Carbon nanotubes can have a range of diameters of about 0.7 nm and larger. The mechanical properties of single tubes have very high strength, stiffness, and elongation making them one of the most impressive structural materials known. Carbon nanotubes have been made using several techniques such as arc-discharge and laser ablation to generate carbon plasma followed by a controlled catalytic deposition, sometimes done in a furnace. There are two main types of carbon nanotubes:
single-wall carbon nanotubes (SWCNT) and multi-wall carbon nanotubes (MWCNT). A SWCNT appears as a single filament of material and has superior mechanical behavior to the MWCNT type. A MWCNT is a collection of carbon nanotubes nested inside other carbon nanotubes to make a sheathed tube. The absence of chemical bonding between nested tubes results in slippage between layered tubes that does not allow translation of load to occur effectively in the radial direction of the tube. Furthermore, since a MWCNT is larger in diameter than a SWCNT, the aspect ratio is smaller resulting in larger cross sectional area and lower specific strength. Different morphologies of SWCNT have been demonstrated. Some of these morphologies are tangled webs, aligned filaments, bundles, ropes, and crystals.
Polycrystalline Diamond is a carbon allotrope that has sp3 hybridization and a continuous 3-dimensional structure of carbon atoms. Diamond is one of the hardest materials known. Due to the potential applications for this material, techniques for vapor phase deposition of diamond have been developed and advanced. Recent developments have led to the formation of nanocrystalline diamond as a domain of diamond material in a second phase of graphitic carbon. Diamondoids have recently been discovered, which are very small crystals of diamond, 4–11 crystal cages of carbon in size. Diamondoids are essentially small particles of diamond that have been identified as possible building blocks for nano-structured materials.
Diamond-like carbon (dlc) is a broad class of amorphous materials having sp2 and sp3 -hybridized carbon and hygrogen. The physical and chemical properties of dlc are between diamond and graphite. The most notable feature of dlc is high hardness. Techniques for vapor phase deposition of dlc have been advanced recently.
Amorphous carbon describes a disordered, three-dimensional material with random sp2 and sp3 hybridization. Amorphous graphite is similar but consists mostly of sp2 hybridization having random stacking of graphitic layer segments. Hydrogenated amorphous carbon is a dlc with a significant fraction of sp3 hybridization.
While graphite is a commonly known form of carbon, there are many types of graphite with a wide range of properties and applications. Graphite is a layered, planar form of carbon bonded in a hexagonal array with sp2 hybridization. The different types of graphite typically describe the degree of order of the planar layers, the flatness of the planar layers, and the distance between the planar layers. Amorphous graphite has been described above and has little order and a relatively large interlaminar spacing. When this material has curved and twisted planar layers it is called tubostratic graphite. Highly Oriented Pyrolytic Graphite (HOPG) is a synthetic material with nearly perfect planar structure that is very ordered with a minimum interlaminar spacing. The term graphene describes a single sheet of graphite, so order is not significant and layer spacing is large enough that it is essentially irrelevant. A graphene platelet is a single small layer of material. Graphitic polyhedral crystals have been reported which resemble a very large MWCNT with a high degree of order and small interlaminar spacing, but the layers are not strictly flat. The graphite layers wrap consistently around a polyhedral core to form a crystal shaped structure. Graphite whiskers, also called vapor grown carbon fibers, have a tree ring concentric cylinder morphology which is similar to the polyhedral graphitic crystals, but are formed about around a circular core to make a fibrous shape.
Often carbon and graphite are used as reinforcement in a composite system. A composite is a combination of two or more different materials that form a single material. Composites typically are hard, strong, or stiff fibers or particles which serve as reinforcement to a softer, more compliant material. An alloy is traditionally used to describe blends of different metals to make a material with designed properties. Similarly, in polymer science, an alloy is a blend of different polymers which is designed to have desirable properties. In both of these definitions of an alloy, two or more similar materials are mixed together in solid solution to form a single material. Therefore, a combination of different carbon allotropes is not a composite, but is strictly an alloy material. Although these prior art types of materials are useful, it would be even more desirable to have a composition of matter comprising a pure carbon isotropic alloy having properties that exceed those of prior art alloys.